1. Field of the Invention
The invention relates to a semiconductor plasma chamber, and more particularly, to a method for dry cleaning a plasma chamber after metal etching to extend the preventive maintenance (PM) cycle.
2. Description of the Related Art
Since metal layers patterned by a plasma processing (dry etching) process offers better critical dimension control than conventional wet chemical etching in the fabrication of microelectronic devices, plasma etching technology is widely applied in the semiconductor and thin film transistor-liquid crystal display (TFT-LCD) industry. Dry etching injects process gas into a chamber having radiation frequency (RF) power, thereby forming RF plasma to serve as an etchant.
During dry etching in the plasma chamber, some etching by-products are deposited on the inner wall of the chamber. When the thickness of deposited etching by-products reaches a certain thickness, the by-products may peel off the inner wall and contaminate the chamber. For example, in the fabrication of a TFT-LCD array, the gate line material is a molybdenum-aluminum-neodymium (MoAlNd) alloy. The MoAlNd alloy layer is etched by a plasma etching process employing chlorine (Cl2) and boron chloride (BCl3) as process gases. In such a process gases easily react with the photoresist pattern layer over the metal layer, forming carbon, aluminum, and molybdenum-containing photoresist residues and aluminum-based compounds, such as aluminum-based chloride (AlCl3), to be deposited on the inner wall of the chamber. The etching by-products deposited on the inner wall of the chamber reduces process stability. That is, the residue may peel off the inner wall of the chamber and fall onto the glass substrate, causing irreparable defects, such as gate line short. Accordingly, it is important to remove such deposited etching by-products.
The conventional method for cleaning the plasma chamber is to open the chamber and then disassemble the components therein. Thereafter, the etching by-products are removed by a physical or chemical method. For example, using deionized water (DIW) and isopropanol (IPA) to clean the components and inner wall of the chamber. However, such a wet cleaning approach is time-consuming and shortens the preventive maintenance (PM) cycle, resulting in the disadvantage of reduced throughput.